Go this from support:
In Brief: An issue with Google Chromecast and Google Home devices has been identified. It is affecting multiple router brands including Verizon's FiOS Quantum Gateway. Details If users are mentioning device connectivity problems on the 5GHz radio and they have Google Chromecast or Google Home hardware, it is possible that these Google devices are impacting the connectivity of other devices. Chromecast devices occasionally generate large amounts of traffic after returning from sleep states. This traffic can be misread by routers as malicious and block traffic on the Wi-Fi network. Workaround: Consistent device connection should be restored by turning off their Chromecast and Google Home devices when they are not in use, instead of allowing them to enter sleep mode. Allow 1-2 minutes after powering off any Chromecast devices in the home for other devices to reconnect. Reboot the router if there is no apparent change. Fix Google has identified the issue and will release a fix to roll out as a Google Play service update. Google Support Page